1. Field of the Invention
The present invention relates to a rotary brake part for a vehicle, and more particularly, to a rotary brake part which is rotated with the wheels of the vehicle and is brought into friction contact with a friction member during a braking operation of the vehicle. This type of the rotary brake part corresponds to a brake drum and a brake disk.
2. Description of the Prior Art
There is a conventionally known brake drum which is formed of an aluminum alloy composite material having excellent wear and heat resistances due to the demand for a reduction in weight of the brake drum.
However, when the brake drum formed of the aluminum alloy composite material is combined with a conventional friction member made of a cast iron for the drum, the problem arises in that the friction coefficient is reduced and for this reason, the brake effectiveness is reduced.
Therefore, it is a conventional practice to replace the friction member by a member having a strong attacking property to the friction contact surface forming section of the brake drum by inclusion of a large amount of an abrasive material or the like. However, if such a measure is employed, since the brake drum has a structure in which a worn powder containing the abrasive material and falling dispersions (e.g., SiC grains) are difficult to discharge out from the drum, there arises a new problem in that the worn powder and the like are liable to stay in the drum, and the wearing of the friction contact surface forming section of the brake drum and the friction member becomes excessive due to the abrading action of the worn powder and the like.
The abrading action of the worn powder and the like is varied in level, but causes a problem even in a brake disk having a good worn powder-discharging characteristic.